Control method of exhaust gas purification system and exhaust gas purification system

ABSTRACT

In forced regeneration control of an exhaust gas purification device a number of data for injection control, such as a number of meshes of a data map and a number of data maps for multi injection control, is decreased while occurrence of torque shock, which is a rapid fluctuation of a generated torque, is avoided. In this forced regeneration control, when an operation state of an internal combustion engine is a high-load operation state, the normal injection control by stopping the multi injection is carried out and, according to a rotation speed and a load of the internal combustion engine, a region for control is divided into a multi-injection control region, a transition region, and a normal injection control region. In the transition region, data for injection control obtained by interpolation of data for injection control on the multi-injection control region side and data for injection control on the normal injection control region side is used.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. Section 371, of PCTInternational Application Number PCT/JP2007/059867, filed May 14, 2007and Japanese Application No. 2006-163038 filed Jun. 13, 2006 in Japan,the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a control method of exhaust gaspurification system and an exhaust gas purification system that cansimplify data for control by decreasing the number of meshes and thenumber of data maps of a data map for multi injection control whilepreventing occurrence of a torque shock at forced regeneration controlaccompanying multi injection of an exhaust gas purification device suchas a continuous regeneration type DPF device or an NOx purificationdevice.

DESCRIPTION OF THE RELATED ART

Regulations on emissions of the particulate matter (PM: particulatematter: Hereinafter referred to as PM) as well as NOx, CO, HC and thelike exhausted from a diesel engine have been tightened year by year. Atechnology has been developed that the PM is trapped by a filter calleda diesel particulate filter (DPF: Diesel Particulate Filter: Hereinafterreferred to as DPF) so as to reduce the PM amount exhausted to theoutside. A continuous regeneration type DPF device carrying a catalystis among them.

This continuous regeneration type DPF device includes an exhaust gaspurification device with an oxidation catalyst device carrying anoxidation catalyst and a DPF device arranged in order from the upstreamside or an exhaust gas purification device with a DPF device carrying anoxidation catalyst arranged and the like. In this device, when atemperature of an exhaust gas flowing into a filter is approximately350° C. or above, the PM trapped by the filter is continuously burnedand purified, and the filter is self-regenerated. However, if thetemperature of the exhaust gas is low, the temperature of a catalyst islowered and the oxidation catalyst is not activated. Thus, the oxidationreaction is not promoted, and oxidation of the PM and regeneration ofthe filter become difficult. As a result, accumulation of PM on thefilter continues and clogging of the filter progresses, which results ina problem of exhaust pressure rise due to the clogging of the filter.

Thus, if the clogging of the filter exceeds a predetermined amount, HC(hydrocarbon) supplied into the exhaust gas by post injection(post-injection) in a cylinder (in-cylinder) and the like is burned bythe oxidation catalyst arranged on the upstream side of the filter orthe oxidation catalyst carried by the filter. Thereby, using thiscombustion heat, the temperature of the exhaust gas at the filter inletor the filter surface is raised. By this high-temperature exhaust gas,the temperature of the filter is raised above a temperature at which thePM accumulated at the filter is burned and the PM is burned and removed.

At this time, if the oxidation catalyst is below an activationtemperature, HC is not oxidized but exhausted as white smoke. Thus, asdescribed in Japanese Patent Application Kokai Publication No.2004-353529, for example, after the temperature of the exhaust gas israised by performing in-cylinder multi-injection (multi-stage delayedinjection) so as to raise the temperature of the exhaust gas so that thetemperature of the oxidation catalyst is raised at the activationtemperature and above, the post injection is carried out. Using theexhaust gas temperature rise by this multi injection, the DPF inlettemperature can be raised while preventing exhaust of the white smoke.

However, in the multi-injection control, since the multi injection isconstituted by stages such as pilot injection, pre injection, maininjection, after injection and the like, data for injection control suchas an injection amount, injection timing and the like are required forinjection at each stage. Thus, the number of such data for injectioncontrol becomes extremely large, which leads to a problem that thenumber of preparation processes of the data for injection control andcalculation amounts, calculation time and the like at control becomelarge. Therefore, simplification of control by decreasing the number ofmeshes (the number of segments) of a base map of the data for injectioncontrol and the number of data maps for environmental correction and thelike is in demand.

In relation to the above, obtaining a finding that the temperature ofthe exhaust gas exhausted from an exhaust manifold is raised when anengine is in a high-load operation state, the inventors have reached thefollowing idea. In the forced regeneration control, when the engine isin the high-load operation state, the temperature of the exhaust gas israised in a normal operation without performing the multi injection, andthe multi injection does not have to be performed. Therefore, bystopping the multi injection and carrying out the normal injection inthis high-load operation state, a portion of the high-load operationstate in the data map of the data for injection control of the multiinjection can be substituted by the data map for normal operation. As aresult, the data for injection control of the multi injection in thehigh-load operation state is not needed any more, and reduction of thedata for control can be promoted.

That is, by means of control of stopping the multi injection andswitching to the normal injection when the high-load operation state isbrought about during the forced regeneration control or the state ischanged to the high-load operation in the middle of the forcedregeneration control, the multi injection control in the high-loadoperation state can be eliminated, and controllability can be improved.Even if the temperature of the exhaust gas exhausted from the exhaustmanifold is raised to some degree, since it might take time till thefilter inlet temperature at the downstream side of the oxidationcatalyst is raised, there is a case in which the exhaust gas temperaturerise control should be continued even in the high-load operation state.

However, since the forced regeneration control might be executed duringtravelling or stopping work, the engine operation state during theforced regeneration control is not always constant. In the exhaust gastemperature rise control, there are a case of low-load/medium-loadoperation states requiring the multi injection, a case of the high-loadoperation state not requiring the multi injection or a case oftransition between these states. If the multi injection is switched tothe normal injection or vice versa at such transition, since a torquegeneration amount is different between the multi injection and thenormal injection and since the state is a high-load operation, there isa problem that a torque shock occurs that causes a large fluctuation ina generated torque of an engine at the switching.

On the other hand, as a general measure against the torque shock, asdescribed in Japanese Patent Application Kokai Publication No.2003-201899, a compression ignition type internal combustion engine isproposed in which a predetermined moderating control is executed for achange amount with a target value of a fuel injection amount at theswitching of a fuel injection mode between a low heat rate pilot/maininjection mode (first injection mode) and a normal injection mode(second injection mode) other than that. However, the generallypracticed moderating control is a control for gradually changing acontrol target amount such as the present injection amount, injectiontiming and the like to a new control target amount over time and doesnot lead to quantitative simplification of the control data fordetermining a control target amount value.

SUMMARY OF THE INVENTION

The present invention was made in order to solve the above problems andhas an object to provide a control method of exhaust gas purificationsystem and an exhaust gas purification system that can reduce the numberof data for injection control such as the number of meshes of a data mapfor multi injection control and the number of data maps and the likewhile avoiding occurrence of a torque shock, which is a suddenfluctuation of a generated torque in forced regeneration control of anexhaust gas purification device such as a continuous regeneration typeDPF, an NOx purification device and the like.

The exhaust gas purification method for achieving the above object is,in a control method of an exhaust gas purification system including anexhaust gas purification device having an oxidation catalyst devicecarrying an oxidation catalyst on the upstream side or an exhaust gaspurification device carrying an oxidation catalyst in an exhaust passageof an internal combustion engine and a controller for carrying outforced regeneration control for recovering purification capability ofthe exhaust gas purification device, in which at forced regenerationcontrol, the controller executes the multi injection control in order toraise a temperature of an exhaust gas, characterized in that at theforced regeneration control, if an operation state of the internalcombustion engine is a high-load operation state, normal injectioncontrol is executed by stopping the multi injection, a region forcontrol is divided into a multi-injection control region, a transitionregion, and a normal injection control region according to a rotationspeed and a load of the internal combustion engine, and in thetransition region, in-cylinder fuel injection is carried out using datafor injection control obtained by interpolation of data for injectioncontrol of the multi-injection control on the multi-injection controlregion side and data for injection control of the normal injectioncontrol on the normal injection control region side.

Moreover, in the above control method of exhaust gas purificationsystem, the interpolation in the transition region is performed suchthat if there are i=1 to I pieces (i, I are positive numbers) of dataF(i) for injection control, based on a load Qm at a rotation speed Nemof the internal combustion engine, supposing that a load and data forinjection control at a boundary on the multi-injection control regionside at the rotation speed Nem are Qml and Fml(i), and that a load anddata for injection control at a boundary on the normal injection controlregion side at the rotation speed Nem are Qnl and Fnl(i), the data forinjection control Ft(i) calculated byFt(i)=((Qnl−Qm)×Fml(i)+(Qm−Qml)×Fnl(i)/(Qnl−Qml) is set as the data F(i)for injection control in the transition region.

Also, in the above control method of exhaust gas purification system, asthe data F(i) for injection control in the transition region, either oneor both of an injection amount and injection timing at each stageinjected during 1 cycle of each cylinder are employed. The each stageincludes pilot injection, pre injection, main injection, after injectionand the like.

Also, in the above control method of exhaust gas purification system, atotal fuel injection amount injected during one cycle of each cylinderis used instead of the load.

The high-load operation state refers to an operation state of aninternal combustion engine in which a load is relatively large and anexhaust temperature, which is a temperature of an exhaust gas exhaustedfrom cylinders is higher than a predetermined temperature. On thecontrol, the high-load operation state can be considered as an operationstate in which a load, which is an engine output required for aninternal combustion engine is above a predetermined load determinedaccording to a rotation speed of the internal combustion engine. Thispredetermined load can be set in advance by experiments, calculation andthe like and inputted and stored in the controller.

And whether a state is the high-load operation state or not can bedetermined by referring to a data map based on the engine rotation speedand the load of the internal combustion engine. Instead of the load, anoutput from an accelerator sensor, a fuel injection amount necessary toexert a required engine output, a total fuel injection amount injectedinto a cylinder and the like may be used. These injection amounts are anamount injected during 1 cycle of each cylinder.

According to the above control method, in the high-load operation state,since the exhaust gas temperature exhausted from the exhaust manifold ofthe internal combustion engine is raised, there is no need to carry outthe multi injection for raising the exhaust gas temperature in order toraise or maintain a temperature of a catalyst or an exhaust gaspurification device. In view of the above, at the forced regenerationcontrol, if an operation state of an internal combustion engine isbrought into a high-load operation state, control to stop themulti-injection control and to change to the normal injection control isexecuted. As a result, in a data map of data for injection control ofthe multi-injection control, a portion of the high-load operation statecan be substituted by data map and the like of data for injectioncontrol of normal operation (operation state not in the forcedregeneration control) in which the normal injection control is carriedout. Thus, the portion of the high-load operation state of the data mapand the like of the data for injection control of the multi-injectioncontrol is not needed any more. Therefore, the number of meshes of thedata map for the multi-injection control and the like can be reduced,and the number of data maps and the like for environmental correctionand the like can be also reduced. The data maps for environmentalcorrection relate to atmospheric temperature, atmospheric pressure, thetemperature of engine-cooling-water temperature, operating states ofother auxiliary machines and the like.

Also, in the above control method, a transition region is providedbetween a multi-injection control region in which the multi-injection(multi-stage injection) control for raising an exhaust gas temperatureis carried out when the exhaust gas temperature is low according to aload of the internal combustion engine and a normal injection controlregion corresponding to the high-load operation state in whichtemperature rise by the multi-injection control is not required. Duringthe forced regeneration control, when the operation state of theinternal combustion engine is changed into the transition region fromthe multi-injection control region due to increase of a load of theinternal combustion engine, weighting is applied according to a positionin the transition region and the data for injection control in thetransition region is acquired by interpolating the data for injectioncontrol in the both regions.

In this transition region, using the data for injection control obtainedby interpolation, in-cylinder fuel injection is carried out. As aresult, since the in-cylinder fuel injection is gradually and smoothlyswitched from the multi injection to the normal injection with a changein the load, occurrence of a torque shock can be avoided. At the sametime, since the data for injection control in the transition region isnot needed any more, the number of data for injection control such asthe number of meshes of the data map, the number of data maps and thelike can be also reduced in this point. With regard to theinterpolation, various interpolation methods can be used, but if linearinterpolation (interpolation by a linear expression) is used, the numberof data required for the interpolation is small, calculation becomeseasy, and control is simplified.

Also, the exhaust gas purification system for achieving the above objectis, in a control method of an exhaust gas purification system includingan exhaust gas purification device having an oxidation catalyst devicecarrying an oxidation catalyst on the upstream side or an exhaust gaspurification device carrying an oxidation catalyst in an exhaust passageof an internal combustion engine and a controller for carrying outforced regeneration control for recovering purification capability ofthe exhaust gas purification device, in which at forced regenerationcontrol, the controller executes the multi injection control in order toraise an exhaust temperature, characterized in that at the forcedregeneration control, the controller executes the normal injectioncontrol by stopping the multi injection when the operation state of theinternal combustion engine is a high-load operation state and accordingto a rotation speed and a load of the internal combustion engine, aregion for control is divided into a multi-injection control region, atransition region, and a normal injection control region, and in thetransition region, using data for injection control obtained byinterpolation of the data for injection control of the multi injectioncontrol on the multi injection control region side and data forinjection control of the normal injection control on the normalinjection control region side, in-cylinder fuel injection is carriedout.

Moreover, in the above exhaust gas purification system, the controlleris configured to perform the interpolation in the transition region suchthat if there are i=1 to I pieces of data F(i) for injection control,based on a load Qm at a rotation speed Nem of the internal combustionengine, supposing that a load and data for injection control at aboundary on the multi-injection control region side at the rotationspeed Nem are Qml and Fml(i), and that a load and data for injectioncontrol at a boundary on the normal injection control region side at therotation speed Nem are Qnl and Fnl(i), the data for injection controlFt(i) calculated by Ft(i)=((Qnl−Qm)×Fml(i)+(Qm−Qml)×Fnl(i)/(Qnl−Qml) isset as the data F(i) for injection control in the transition region.

Also, in the above exhaust gas purification system, the controller isconfigured such that as the data F(i) for injection control in thetransition region, either one or both of an injection amount andinjection timing at each stage injected during one cycle of eachcylinder are employed.

Also, in the above exhaust gas purification system, the controller isconfigured such that a total fuel injection amount injected during 1cycle of each cylinder is used instead of the load.

According to the exhaust gas purification system with the aboveconfiguration, the above exhaust gas purification method can be put intopractice and the similar effect can be obtained. Also, the exhaust gaspurification device includes not only the continuous regeneration typeDPF but also an NOx purification device such as a NOx occlusion andreduction type catalyst or NOx direct reduction type catalyst and thelike carrying out the similar forced regeneration control. Moreover,since the application range of the present invention can also includethe forced regeneration control and the like such as recovery fromsulfur poisoning, forced regeneration control and the like to the sulfurpoisoning and the like of an exhaust gas purification device providedwith not only the NOx occlusion and reduction type catalyst or NOxdirect reduction type catalyst but also a selective reduction type (SCR)catalyst and the like are included. Essentially, any exhaust gaspurification system carrying out the control similar to the above iswithin the application range of the present invention.

Advantages of the Invention

According to the control method of exhaust gas purification system andthe exhaust gas purification system according to the present invention,since in the forced regeneration control of the exhaust gas purificationdevice such as a continuous regeneration type DPF device, an NOxpurification device and the like, data for injection control of normaloperation control, which is not the forced regeneration control, can beused in a portion for the normal injection control region correspondingto the high-load operation state, data for injection control for themulti-injection control is reduced.

Also, in the forced regeneration control, even at transition between themulti-injection control region in which the operation state of theinternal combustion engine requires multi-injection and the normalinjection control region not requiring the multi injection, a transitionregion is provided so that the in-cylinder fuel injection can besmoothly changed, and occurrence of torque shock can be prevented.

Moreover, since the interpolation is used in this transition region,data for injection control for the multi-injection control in thetransition region is not needed, either. Therefore, the number of meshesof the data map of the data for the multi-injection control in theforced regeneration control, the data map for environmental correctionand the like can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an entire configuration of an exhaustgas purification system.

FIG. 2 is a diagram schematically illustrating an example of a regiondata map.

FIG. 3 is a diagram illustrating an example of a control flow of forcedregeneration control.

FIG. 4 is a diagram illustrating an example of a control flow forcalculating data for injection control.

FIG. 5 is a diagram illustrating another example of a control flow forcalculating data for injection control.

FIG. 6 is a diagram schematically illustrating each state of in-cylinderfuel injection.

EXPLANATION OF REFERENCE NUMERALS

-   1: exhaust gas purification system-   10: diesel engine (internal combustion engine)-   12: continuous regeneration type DPF device (exhaust gas    purification device)-   12 a: oxidation catalyst-   12 b: filter with catalyst-   31: differential pressure sensor-   40: controller (ECU)-   F(i): data for injection control of transition region-   Fm(i): data for injection control for multi injection-   Fml(i): data for injection control at boundary on the    multi-injection control region side-   Fn(i): data for injection control for normal injection-   Fnl(i): data for injection control at boundary on the normal    injection region side-   Ft(i): data for injection control for interpolation-   Lm: boundary on the multi-injection control region side-   Ln: boundary on the normal injection region side-   Ne, Nem: engine rotation speed-   Q, Qm: engine load-   Qml: load at boundary on the multi-injection control region side-   Qnl: load at boundary on the normal injection region side-   Rm: multi injection control region-   Rn: normal injection control region-   Rt: transition region

DESCRIPTION OF THE EMBODIMENTS

The control method of exhaust gas purification system and an exhaust gaspurification system of an embodiment according to the present inventionwill be described referring to the attached drawings using a continuousregeneration type DPF (Diesel Particulate Filter) as an example. FIG. 1shows configuration of an exhaust gas purification system 1 of thisembodiment.

The exhaust gas purification system 1 includes an exhaust gaspurification device 12 in an exhaust passage 11 of a diesel engine(internal combustion engine) 10. This exhaust gas purification device 12is one of continuous regeneration type DPF devices and includes anoxidation catalyst device 12 a on the upstream side and a filter device12 b with catalyst on the downstream side. Moreover, on the downstreamside of the exhaust gas purification device 12, a silencer 13 isprovided. Also, on the upstream side of the exhaust gas purificationdevice 12, an exhaust brake valve (exhaust brake) 14 is provided, whileon the downstream side, an exhaust throttle valve (exhaust throttle) 15is provided.

The oxidation catalyst device 12 a is formed by having an oxidationcatalyst such as platinum (Pt) carried by a carrier such as a porousceramic honeycomb structure. The filter device 12 b with catalyst isformed by a monolith-honeycomb wall-flow type filter and the like inwhich an inlet and an outlet of a channel of a porous ceramic honeycombare alternately sealed. A catalyst of platinum, cerium oxide and thelike is carried in this filter portion. PM (particulate matter) in theexhaust gas G is trapped by a wall of the porous ceramic.

In order to estimate an accumulated amount of the PM in the filterdevice 12 b with catalyst, a differential pressure sensor 31 is providedin a conduit connected to before and after the exhaust gas purificationdevice 12. Also, for regeneration control of the filter device 12 b withcatalyst, an oxidation-catalyst inlet exhaust-temperature sensor 32 isprovided on the upstream side of the oxidation catalyst device 12 a anda filter inlet exhaust-temperature sensor 33 is provided between theoxidation catalyst device 12 a and the filter device 12 b with catalyst.

This oxidation-catalyst inlet exhaust-temperature sensor 32 detects afirst exhaust gas temperature Tg1, which is a temperature of the exhaustgas flowing into the oxidation catalyst device 12 a. The filter inletexhaust-temperature sensor 33 detects a second exhaust gas temperatureTg2, which is a temperature of the exhaust gas flowing into the filterdevice 12 b with catalyst.

Moreover, in an intake passage 16, an air cleaner 17, an MAF sensor(intake air amount sensor) 18, an intake throttle valve (intakethrottle) 19 and the like are provided. The intake throttle valve 19adjusts an amount of an intake A into an intake manifold. At an EGRpassage 20, an EGR cooler 21 and an EGR valve 22 are provided.

Output values of these sensors are inputted to a controller (ECU: EngineControl Unit) 40 for general control of operation of the engine 10 aswell as regeneration control of the exhaust gas purification device 12.By control signals outputted from the controller 40, the intake throttlevalve 19, a fuel injection device (injection nozzle) 23, the exhaustbrake valve 14, an exhaust throttle valve 15, the EGR valve 22 and thelike are controlled.

The fuel injection device 23 is connected to a common rail injectionsystem 27 temporarily reserving high-pressure fuel whose pressure hasbeen raised by a fuel pump (not shown). Into the controller 40,information such as a vehicle speed, cooling water temperature and thelike in addition to information such as acceleration opening from anaccelerator position sensor (APS) 34, engine rotation speed from anengine speed sensor 35, a common rail pressure from a rail pressuresensor 36 and the like are inputted for operation of the engine. Thecontroller 40 also outputs electrification time signals so that apredetermined amount of fuel is injected from the fuel injection device23.

In the regeneration control of the exhaust gas purification device 12,not only for automatic forced regeneration during running but also forforced regeneration arbitrarily performed by a driver after stopping thevehicle, a flashing lamp (DPF lamp) 24, an alarm lamp 25 lighted atabnormality, and a manual regeneration button (manual regenerationswitch) 26 are provided. The flashing lamp 24 and the alarm lamp 25 atabnormality are warning means for drawing attention of a driver when atrapped amount of PM in the filter device 12 b with catalyst exceeds agiven amount and the filter device 12 b with catalyst is clogged.

Next, control of the exhaust gas purification system 1 will bedescribed. In this control, PM is trapped in normal operation. In thisnormal operation, whether it is time to start the forced regeneration ornot is monitored, and if it is determined that it is time to start theforced regeneration, the forced regeneration control is executed. Thisforced regeneration control includes running automatic regeneration forcarrying out forced regeneration control during running and manualregeneration started by pressing the manual regeneration button 26 afterstopping of a vehicle by a driver upon an alarm. These forcedregeneration controls are selected and executed as appropriate accordingto a traveling distance and a value of DPF differential pressure. Aregeneration controller for carrying out these forced regenerationcontrols is incorporated in the controller 40.

And regarding the forced regeneration such as the manual regenerationand running automatic regeneration, in this embodiment, a first exhaustgas temperature rise control is executed when a catalyst temperatureindex temperature indicating a temperature of the oxidation catalyst 12a (bed temperature) is lower than a predetermined first determiningtemperature Tc1, while a second exhaust gas temperature rise controlinvolving post injection is executed when the temperature is at thepredetermined first determining temperature Tc1 or above. Moreover,temperature maintaining control is executed when a filter temperatureindex temperature indicating a temperature of the filter device 12 bwith catalyst is at a predetermined second determining temperature Tc2or above.

In the present invention, in any of the first exhaust gas temperaturecontrol, second exhaust gas temperature control, and temperaturemaintaining control, as shown in FIG. 2, multi-injection control forexhaust gas temperature rise is executed in a multi-injection controlregion Rm corresponding to a low/medium load operation region, whilenormal injection control without the multi-injection control is executedin a normal injection control region Rn corresponding to a high-loadoperation state. Also, in a transition region Rt provided between themulti-injection control region Rm and the normal injection controlregion Rn, the multi-injection control by data for injection controlacquired by interpolation is executed.

This interpolation is executed as follows. First, a region data mapwhich divides the region of engine control into the multi-injectioncontrol region Rm, the transition region Rt, and the normal injectioncontrol region Rn with respect to a rotation speed Ne (lateral axis) anda load Q (vertical axis) of an internal combustion engine as shown inFIG. 2, is prepared and stored in the controller 40. This region datamap can be set in advance by examining if the exhaust gas temperatureshould be raised by multi injection or not by experiments orcalculations.

Next, from the engine rotation speed Nem and the load Qm detected duringthe forced regeneration control, it is determined in which region of theregion data map shown in FIG. 2 a current engine operation state (atcontrol) is located. That is, when a load at a boundary Lm on themulti-injection control region (low-/medium-load operation state) Rmside at the rotation speed Nem is Qml and a load at a boundary Ln on thenormal injection region (high-load operation state) Rn side is Qnl, ifthe load Qm is not more than the load Qml, it is considered to be in themulti-injection control region Rm, if the load Qm exceeds the load Qmland not more than the load Qnl, it is considered to be in the transitionregion Rt, and if the load Qm exceeds the load Qnl, it is considered tobe in the normal injection control region Rn.

If in the multi-injection control region Rm, the multi-injection controlis executed based on data Fm(i) for injection control calculated fromthe data map for control of the multi injection. If in the normalinjection control region Rn, the normal injection control is executedbased on data Fn(i) for injection control calculated from the data mapfor control of the normal injection.

On the other hand, if in the transition region Rt, in-cylinder fuelinjection is executed using data F(i) for injection control obtained byinterpolation of the data Fml(i) for injection control of the multiinjection at the boundary Lm on the multi-injection control region Rmside at the rotation speed Nem of the engine 10 and the data Fnl(i) forinjection control of the normal injection at the boundary Ln on thenormal injection region Rn side at the rotation speed Nem of the engine10. Here, suppose that there are i=1 to I pieces (here, i and I arepositive numbers) of the data F(i) for injection control. The data F(i)for injection control is data such as an injection amount, injectiontiming and the like of each stage (pilot injection F1, pre injection F2,main injection F3, after injection F4 and the like) injected in 1 cycleof each cylinder as schematically shown in FIG. 6.

The data Fml(i) for injection control of the multi-injection is obtainedby correcting data for control obtained from the base map formulti-injection control with a correction coefficient obtained from thedata map for environmental correction. Also, the data Fnl(i) forinjection control of the normal injection is obtained by correcting thedata for control obtained from the base map for the normal injectioncontrol with a correction coefficient obtained from the data map forenvironmental correction.

If linear interpolation is used as the interpolation, an amount of datafor injection control Ft(i) calculated byFt(i)=((Qnl−Qm)×Fml(i)+(Qm−Qml)×Fnl(i)/(Qnl−Qml) is set as the data F(i)for injection control in the transition region Rt.

Also, in this interpolation, first, an index value t of a position inthe transition region Rt is calculated and interpolation may be executedusing that. The index value t of the position indicates a positioncorresponding to the load Qm by a numeral value from zero to 1 when theposition of the boundary Ln on the normal injection region Rn side iszero and the position of the boundary Lm on the multi injection regionRm side is 1, and it is calculated by t=(Qnl−Qm)/(Qnl−Qml). Next, usingthis t, the amount Ft(i) of the data for injection control calculated byFt(i)=t×Fml(i)+(1−t)×Fnl(i) is made the data F(i) for injection controlin the transition region Rt.

As the amount F (i) of the data for injection control of the transitionregion Rt, it is preferable that both the injection amount and injectiontiming by injection at each stage injected in 1 cycle of each cylinderare selected, but only the data for injection control of a stage withmore influences on the torque shock may be used.

Also, usually, as the region data map as shown in FIG. 2, different datamap is used for the first exhaust gas temperature control, secondexhaust gas temperature control, and temperature maintaining control,respectively. However, for further simplification of control, the mapdata of the same region may be used in order to reduce the number ofdata maps for control.

Next, the control will be described using control flows in FIGS. 3 to 5.When the control flow in FIG. 3 is started, at Step S11, it isdetermined if control is the forced regeneration control by the runningautomatic regeneration or manual regeneration. If the control is not theforced regeneration control, the forced regeneration control is notexecuted but the routine is returned and the normal operation control isexecuted. If it is determined as the forced regeneration control at StepS11, the routine goes to Step S12.

Whether the control is forced regeneration control or not is determinedas follows. In the case of the forced regeneration control by manualregeneration, when a differential pressure detected by the differentialpressure sensor 31 for measuring a differential pressure before andafter the exhaust gas purification device 12 exceeds a predetermineddifferential pressure value for determination or the like, the flashinglamp (DPF lamp) 23 as alarming means is flashed and the driver ispromoted for manual regeneration of the DPF. When the driver promptedfor the manual regeneration stops the vehicle and operates the manualregeneration button 25, the control becomes the forced regenerationcontrol. In the case of the forced regeneration control in the runningautomatic regeneration, when it is detected from a detection value ofthe differential pressure sensor 31 and the like that a trapped amountof PM in the filter device 12 b with catalyst exceeds a predeterminedamount, the control becomes the forced regeneration control.

At Step S12, the first determining temperature Tc1 is calculated. Thisfirst determining temperature Tc1 is a temperature (approximately 200 to250° C., for example) at which HC, which is an unburned fuel supplied bythe post injection, is sufficiently oxidized by the oxidation catalystof the oxidation catalyst device 12 a if the second exhaust gastemperature (catalyst temperature index temperature) Tg2 becomes thistemperature. This second exhaust gas temperature Tg2 is an exhaust gastemperature detected by the filter inlet exhaust-temperature sensor 33.Also, as the first determining temperature Tc1, a value changingaccording to the engine rotation speed Nem at that time may be used.Also, instead of the second exhaust gas temperature Tg2 detected by thefilter inlet exhaust-temperature sensor 33, the first exhaust gastemperature Tg1 detected by the oxidation-catalyst inlettemperature-sensor 32 may be used.

At the subsequent Step S13, the second exhaust gas temperature (catalysttemperature index temperature) Tg2 is checked. If the second exhaust gastemperature Tg2 is lower than the first determining temperature Tc1calculated at Step S12, the first exhaust gas temperature rise controlis carried out at Step S14 for a predetermined time (time relating to aninterval of check of the second exhaust gas temperature Tg2 at Step S13)Δt1. After Step S13, the routine returns to Step S12.

If it is determined at Step S13 that the second exhaust gas temperatureTg2 is at the predetermined first determining temperature Tc1 or above,the routine goes to Step S15. At Step S15, the second determiningtemperature Tc2 is calculated. The second determining temperature Tc2 isa target temperature for the second exhaust gas temperature rise controlat Step S17. By maintaining the second exhaust gas temperature (filtertemperature index temperature) Tg2 at the temperature Tc2 or above,combustion of the PM trapped in the filter device 12 b with catalyst ismaintained in a favorable state. The second exhaust gas temperature Tg2is a temperature of an exhaust gas detected by the filter inletexhaust-temperature sensor 33. The second determining temperature Tc2 isusually set at a value higher than a combustion start temperature of thePM (approximately 350° C., for example), at approximately 500° C., forexample. The value of the second determining temperature Tc2 may bechanged in multi-stages according to time.

At the subsequent Step S16, the second exhaust gas temperature (filtertemperature index temperature) Tg2 is checked. If the second exhaust gastemperature Tg2 is lower than the second determining temperature Tc2,the routine goes to the second exhaust gas temperature rise control atStep S17, while if the second exhaust gas temperature Tg2 is at thesecond determining temperature Tc2 or above, the routine goes to thetemperature maintaining control at Step S18.

At Step S17, the second exhaust gas temperature rise control isconducted for a predetermined time (time relating to an interval ofcheck of the second exhaust gas temperature Tg2 at Step S16) Δt2.

The exhaust gas temperature rise is continued by the second exhaust gastemperature rise control and at the same time, unburned fuel (HC) issupplied into the exhaust gas by the post injection. This unburned fuelis oxidized by the oxidation catalyst device 12 a, and the exhaust gastemperature can be further raised by this oxidation heat. If the raisedexhaust gas temperature Tg2 becomes at the second determiningtemperature Tc2 or above, the PM trapped by the filter device 12 b withcatalyst is burned. The second exhaust gas temperature Tg2 may becontinuously raised to the temperature Tc2 as a control target by thissecond exhaust gas temperature rise control, but the temperature may beraised in two stages or multi-stages. After the Step S17, the routinegoes to Step S19.

If it is determined at Step S16 that the second exhaust gas temperatureTg2 is at the second determining temperature Tc2 or above, thetemperature maintaining control without post injection in thein-cylinder injection of the engine 10 conducted for a predeterminedtime (time relating to an interval of duration time check of the secondexhaust gas temperature Tg2 at Step S16) Δt3 at Step S18.

Also, at Step S18, PM combustion cumulative time is counted. In thiscount, only if the second exhaust gas temperature Tg2 is at thepredetermined second determining temperature Tc2 or above, the PMcombustion cumulative time ta is counted (ta=ta+Δt3). After Step S18,the routine goes to Step S19.

At Step S19, in order to determine if the forced regeneration control isto be finished or not, the PM combustion cumulative time ta is checked.In this check, it is checked if the PM combustion cumulative time taexceeds a predetermined determining time Tac or not. That is, if it isexceeded, the regeneration control is considered to be completed, andthe routine goes to Step S20, while if not exceeded, the regenerationcontrol is considered not to be completed, and the routine returns toStep S12. Till the PM combustion cumulative time ta exceeds thepredetermined determining time tac, the first exhaust gas temperaturerise control at Step S14, the second exhaust gas temperature risecontrol at Step S17 or the temperature maintaining control at Step S18is carried out.

At Step S20, the forced regeneration control is finished, and if thevehicle is parked, the exhaust brake valve 13 and the exhaust throttlevalve 14 are returned to the normal operation state and the routinereturns to the normal injection control. And then, it returns.

In the control flow in FIG. 3, if the catalyst temperature indextemperature Tg2 indicating the oxidation catalyst temperature (bedtemperature) is lower than the predetermined first determiningtemperature Tc1, the first exhaust gas temperature rise control isexecuted, while if the temperature becomes at the predetermined firstdetermining temperature Tc1 or above, the second exhaust gas temperaturerise control with post injection is carried out. Moreover, if the filtertemperature index temperature indicating the temperature of the filterdevice 12 b with catalyst becomes the predetermined second determiningtemperature Tc2 or above, the temperature maintaining control isexecuted.

In the control flow in FIG. 3, as the catalyst temperature indextemperature indicating the temperature of the oxidation catalyst 12 a(bed temperature), the second exhaust gas temperature Tg2 detected bythe filter inlet exhaust temperature sensor 33 is used, and as thefilter temperature index temperature indicating the temperature of thefilter device 12 b with catalyst, too, the second exhaust gastemperature Tg2 detected by the filter inlet exhaust temperature sensor33 is used. However, as the catalyst temperature index temperatureindicating the temperature of the oxidation catalyst 12 a (bedtemperature), the first exhaust gas temperature Tg1 detected by theoxidation-catalyst inlet exhaust temperature sensor 32 may be used.

And in the present invention, in the first exhaust gas temperature risecontrol at Step S14, the second exhaust gas temperature rise control atStep S17, and the temperature maintaining control at Step S18, themulti-injection control is executed in the low-/medium-load operationregion but in the high-load operation state, the normal injectioncontrol without multi-injection is carried out.

This control can be conducted according to the control flow as shown inFIGS. 4 and 5. The control flow shown in FIGS. 4 and 5 is called whenthe data F(i) for injection control of in-cylinder fuel injection isrequired when the first exhaust gas temperature rise control, secondexhaust gas temperature rise control, temperature maintaining control isstarted, and the data F(i) for injection control is calculated by thiscontrol flow and the routine returns to a location where the controlflow is called after the calculation.

When the control flow in FIG. 4 is started, the engine rotation speedNem and the load Qm indicating the operation state of the engine 10 areinputted at Step S31. At Step S32, the load Qml at the boundary Lm onthe multi-injection control region Rm side at the rotation speed Nem ofthe engine 10 and the load Qnl at the boundary Ln on the normalinjection region Rn side are inputted at Step S32.

At the subsequent Step S33, the load Qm is checked and it is determinedif the load is not more than the load Qml or not. If the load Qm is notmore than the load Qml in this determination, the routine goes to StepS34, where i=1 to I pieces of the data F(i) for injection control ismade the data Fm(i) for injection control calculated from the data mapof the multi injection base and the data map for environmentalcorrection and the routine returns.

If the load Qm is not the load Qml or less in the determination at StepS33, the routine goes to Step S35, where the load Qm is checked and itis determined if the load is not less than the load Qnl or not. If theload Qm is not less than the load Qnl in this determination, the routinegoes to Step S36, where i=1 to I pieces of the data F(i) for injectioncontrol is made the data Fn(i) for injection control calculated from thedata map of the normal injection base in the normal operation and thedata map for environmental correction and the routine returns.

If the load Qm is not the load Qnl or more in the determination at StepS35, the routine goes to Step S37. At Step S37, i=1 to I pieces of thedata Fml(i) for injection control of the multi injection at the boundaryLm on the multi-injection control region Rm side at the rotation speedNem of the engine 10 and the data Fnl(i) for injection control of thenormal injection at the boundary Ln on the normal injection region Rnside at the rotation speed Nem of the engine 10 are inputted.

At the subsequent Step S38, i=1 to I pieces of the data Ft(i) forinjection control of the interpolation are calculated byFt(i)=((Qnl−Qm)×Fml(i)+(Qm−Qml)×Fnl(i))/(Qnl−Qml). At the subsequentStep S39, i=1 to I pieces of F(i) is made Ft(i) and the routine returns.

Here, in this interpolation, if the index value t of the position in thetransition region Rt is used, as shown in the control flow in FIG. 5, itis constituted by Step S38 a and Step S38 b instead of Step S38. At StepS38 a, the index value t of the position is calculated byt=(Qnl−Qm)/(Qnl−Qml). At Step S38 b, using the index value t of theposition, the data Ft(i) for injection control is calculated byFt(i)=t×Fml(i)+(1−t)×Fnl(i).

According to the control flow in FIGS. 4 and 5, in the forcedregeneration control, the following control can be conducted. If theoperation state of the engine 10 is a high-load operation state, thenormal injection control by stopping the multi injection is carried out.At the same time according to the rotation speed Nem and the load Qm ofthe engine 10, the region for control is divided into themulti-injection control region Rm, the transition region Rt, and thenormal injection control region Rn. In the transition region Rt, usingthe data Ft(i) for injection control obtained by interpolation of thedata Fml(i) for injection control of the multi-injection control at theboundary Lm on the multi-injection control region Rm side and the dataFnl(i) for injection control of the normal injection control at theboundary Ln on the normal injection control region Rn side, thein-cylinder fuel injection is carried out.

Also, in the interpolation in the transition region Rt, if there are i=1to I pieces of data F(i) for injection control, the data Ft(i) forinjection control calculated byFt(i)=((Qnl−Qm)×Fml(i)+(Qm−Qml)×Fnl(i)/(Qnl−Qml) may be made the dataF(i) for injection control in the transition region Rt. Here, based onthe load Qm at the rotation speed Nem of the engine 10, the load and thedata for injection control at the boundary Lm on the multi-injectioncontrol region Rm side at the rotation speed Nem are set as Qml andFml(i), and the load and the data for injection control at the boundaryLn on the normal injection control region Rn side at the rotation speedNem are set as Qnl and Fnl(i).

In the above embodiment, as the exhaust gas purification device of theexhaust gas purification system, combination of the oxidation catalystdevice 12 a on the upstream side and the filter 12 b with catalyst onthe downstream side was used as an example. However, the exhaust gaspurification device may be a filter carrying an oxidation catalyst.Moreover, as the method of supplying the unburned fuel (HC) to theupstream side of the oxidation catalyst 12 a, post injection wasexplained. However, by arranging an unburned fuel supply device in theexhaust passage 16, a method of direct injection into an exhaust pipethat directly injects unburned fuel into the exhaust passage 16 from theunburned fuel supply device may be employed.

Also, as the exhaust gas purification device, not only the continuousregeneration type DPF but also an NOx purification device such as an NOxocclusion and reduction type catalyst or an NOx direct reduction typecatalyst and the like carrying out the similar forced regenerationcontrol may be employed. Moreover, the application range of the presentinvention may include the forced regeneration control and the like fromrecovery from sulfur poisoning and the like. Therefore, the forcedregeneration control and the like to the sulfur poisoning of the exhaustgas purification device provided with not only the NOx occlusion andreduction type catalyst or the NOx direct reduction type catalyst butalso the selective reduction type (SCR) catalyst and the like may beincluded.

The control method of the exhaust gas purification system and theexhaust gas purification system of the present invention having theabove-mentioned excellent effects can be utilized extremely effectivelyfor an exhaust gas purification system provided with an exhaust gaspurification device having an oxidation catalyst device carrying anoxidation catalyst on the upstream side or an exhaust gas purificationdevice carrying an oxidation catalyst and a controller carrying outforced regeneration control for recovering a purification capability ofthe exhaust gas purification device in an exhaust passage of an internalcombustion engine, in which the controller executes multi injectioncontrol for raising an exhaust temperature at the forced regenerationcontrol.

What is claimed is:
 1. A control method of an exhaust gas purificationsystem comprising an exhaust gas purification device having an oxidationcatalyst device carrying an oxidation catalyst on the upstream side oran exhaust gas purification device carrying an oxidation catalyst in anexhaust passage of an internal combustion engine and a controller forcarrying out forced regeneration control for recovering purificationcapability of said exhaust gas purification device, in which at forcedregeneration control the controller executes multi-injection control inorder to raise an exhaust temperature, wherein, in normal operationcontrol, whether it is timing to start the forced regeneration controlor not is monitored, and if it is determined as the timing to start theforced regeneration, the forced regeneration control is executed, and atthe forced regeneration control, a first exhaust gas temperature of anexhaust gas flowing into an oxidation-catalyst device and a secondexhaust gas temperature of the exhaust gas flowing into a filter devicewith the catalyst are detected; and it is judged whether the firstexhaust gas temperature is lower than a predetermined first determiningtemperature and whether the second exhaust gas temperature is at apredetermined second determining temperature or above, wherein, when thefirst exhaust gas temperature is at the first determining temperature orlower, an operation state of a vehicle is verified, and when theoperation state is in a low/medium load operation region, the exhaustgas temperature is raised by a multi-injection control; when theoperation state is in high load operation region, the exhaust gastemperature is raised by a normal injection control; and when theoperation state is in a transition region, the exhaust gas temperatureis raised by use of interpolation data, wherein, at the forcedregeneration control, when the first exhaust gas temperature exceeds thefirst determining temperature as well as when the second exhaust gastemperature is lower than the second determining temperature, theoperation state of a vehicle is verified, and when the operation stateis in a low/medium load operation region, the exhaust gas temperature israised by a multi-injection control; when the operation state is in ahigh load operation region, the exhaust gas temperature is raised by anormal injection control; and when the operation state is in atransition region, the exhaust gas temperature is raised by use ofinterpolation data, and wherein, at the forced regeneration control,when the second exhaust gas temperature is at the second determiningtemperature or above, the operation state of a vehicle is verified, andwhen the operation state is in a low/medium load operation region, theexhaust gas temperature is maintained by a multi-injection control; whenthe operation state is in a high load operation region, the exhaust gastemperature is maintained by a normal injection control; and when theoperation state is in a transition region, the exhaust gas temperatureis maintained by use of interpolation data.
 2. The control methodaccording to claim 1, wherein the interpolation in said transitionregion is performed such that if there are i=1 to I pieces of data F(i)for injection control, based on a load Qm at a rotation speed Nem of theinternal combustion engine, supposing that a load and data for injectioncontrol at a boundary on the multi-injection control region side at therotation speed Nem are Qml and Fml(i), and that a load and data forinjection control at a boundary on the normal injection control regionside at the rotation speed Nem are Qnl and Fnl(i), the data Ft(i) forinjection control calculated byFt(i)=((Qni−Qm)×fml(i)+(Qm−Qml)×Fnl(i))/(Qnl−Qml) is set as the dataF(i) for injection control in said transition region.
 3. The controlmethod according to claim 2, wherein, in the interpolation, as the dataF(i), either one or both of an injection amount and an injection timingat each stage injected during one cycle of each cylinder are employed.4. An exhaust gas purification system in a control method of an exhaustgas purification comprising an exhaust gas purification device having anoxidation catalyst device carrying an oxidation catalyst on the upstreamside or an exhaust gas purification device carrying an oxidationcatalyst in an exhaust passage of an internal combustion engine and acontroller for carrying out forced regeneration control for recoveringpurification capability of the exhaust gas purification device, in whichat forced regeneration control, the controller is programmed to executea multi-injection control in order to raise an exhaust temperature,wherein, in normal operation control, whether it is timing to start theforced regeneration control or not is monitored, and if it is determinedas the timing to start the forced regeneration, the forced regenerationcontrol is executed, and at the forced regeneration control, a firstexhaust gas temperature of an exhaust gas flowing into anoxidation-catalyst device and a second exhaust gas temperature of theexhaust gas flowing into a filter device with the catalyst are detected;and it is judged whether the first exhaust gas temperature is lower thana predetermined first determining temperature and whether the secondexhaust gas temperature is at a predetermined second determiningtemperature or above, wherein, when the first exhaust gas temperature isat the first determining temperature or lower, an operation state of avehicle is verified, and when the operation state is in a low/mediumload operation region, the exhaust gas temperature is raised by amulti-injection control; when the operation state in high load operationregion, the exhaust gas temperature is raised by a normal injectioncontrol; and when the operation state is in a transition region, theexhaust gas temperature is raised by use of interpolation data, wherein,at the forced regeneration control, when the first exhaust gastemperature exceeds the first determining temperature as well as whenthe second exhaust gas temperature is lower than the second determiningtemperature, the operation state of a vehicle is verified, and when theoperation state is in a low/medium load operation region, the exhaustgas temperature is raised by a multi-injection control; when theoperation state is in a high load operation region, the exhaust gastemperature is raised by a normal injection control; and when theoperation state is in a transition region, the exhaust gas temperatureis raised by use of interpolation data, and wherein, at the forcedregeneration control, when the second exhaust gas temperature is at thesecond determining temperature or above, the operation state of avehicle is verified, and when the operation state is in a low/mediumload operation region, the exhaust gas temperature is maintained by amulti-injection control; when the operation state is in a high loadoperation region, the exhaust gas temperature is maintained by a normalinjection control; and when the operation state is in a transitionregion, the exhaust gas temperature is maintained by use ofinterpolation data.
 5. The exhaust gas purification system according toclaim 4, wherein said controller executes the interpolation in saidtransition region such that if there are i=1 to I pieces of data F(i)for injection control, based on a load Qm at a rotation speed Nem of theinternal combustion engine, supposing that a load and data for injectioncontrol at a boundary on the multi-injection control region side at therotation speed Nem are Qml and Fml(i), and that a load and data forinjection control at a boundary on the normal injection control regionside at the rotation speed Nem are Qnl and Fnl(i), the data forinjection control Ft(i) calculated byFt(i)=((Qni−Qm)×fml(i)+(Qm−Qml)×fnl(i))/(Qnl−Qml) is set as the dataF(i) for injection control in said transition region.
 6. The exhaust gaspurification system according to claim 5, wherein said controlleremploys, as the data F(i) either one or both of an injection amount andan injection timing at each stage injected during one cycle of eachcylinder.